This invention relates to a self-propelled tunnel excavation apparatus.
A known tunnel excavation method comprises constructing the final tunnel supporting lining before excavating the earth corresponding to the useful tunnel cross-section.
This method, which enables lining of considerable thickness (30-120 mm) to be achieved, is implemented by constructing a sequence of adjacent cast segments by the opening and closure panel technique. With this technique, each panel is formed by inserting a cutter unit into the earth and forming the concrete casting during the extraction of the tool by a casting tube which passes longitudinally through the cutter unit. The closure segments are made after cutting away a part of the concrete forming the two cast opening segments. The purpose of this operation is to dress the surface of the already hardened concrete of the primary segments to ensure good contact/connection with the fresh closure segment. Dressing is correctly used in construction work on any resumption of concrete casting.
The depth of the cast segments obtained in this manner is about 8.5 meters, after which the earth enclosed by them is excavated to depth of about 7 meters. After this a new series of cast segments is made, followed by excavation.